Introduction
Adding a graphical touch HMI (Human Machine Interface) to a product is a great way to enhance the user experience. But the benefits go way beyond this: It adds flexibility to accommodate new features (both now and in future), helps overcome obsolescence of traditional controls, and enables a family of products to share a common HMI platform with strong brand visibility, while remaining easily customizable and supporting multiple languages.
Thanks to the innovative Embedded Video Engine (EVE) from Bridgetek, designing or updating products with a graphical touch display interface is fast and easy to do, even when the engineers have no prior experience with touch screen graphical HMIs. The graphical display, touch and even audio can be added to the existing MCU over SPI or Quad-SPI (QSPI). Along with extensive design software tools and examples, this solution ensures the product can benefit from the advantages in a short timescale.
Challenges
There are some cases, however, where directly connecting the EVE device to the existing system MCU or controller is not the most feasible option, requiring a slightly different approach. These include:
- Longer Distances – In some applications, the touch display will not be adjacent to the main MCU or to the device being controlled and may be beyond the optimal distance for protocols such as RGB, LVDS, SPI/QSPI and I2C.
- System Architecture and Partitioning – The main product electronics may not be MCU-based or may not have sufficient processing or I/O capacity to support a display controller. It may also be a requirement to minimise or avoid changes to the firmware.
- Time to market – Designing, prototyping and assembling the overall PCB and enclosure, can be a complex and time-consuming process.
In the following sections, we’ll explain how the new Intelligent Display Panels (IDP) from Bridgetek help address these challenges.
Longer Distances
When designing a product with the EVE IC or modules from Bridgetek, the system MCU or controller connects to EVE over SPI or QSPI. EVE then connects to the display via RGB or LVDS, and to the touch panel via I2C (capacitive touch) or analogue signals (resistive touch).
Where the display must be located further from the MCU (for example 2m, 10m or even more than 100m), the distance limitations of the SPI/QSPI communication as well as the RGB/LVDS, analogue and I2C signals can become a challenge. Voltage drop can also be a concern when transferring the typical 5V and 3.3V power supplies over long cables.
Some examples of applications requiring long distances include smart building systems, room and desk booking systems, industrial machines with the display on an articulated arm, and remote-control panels for machines and devices.
Figure 1: The IDP modules are ideal for use cases where there is distance between the HMI and the main system controller
The Intelligent Display Panels (IDP) from Bridgetek provide a robust solution allowing the graphical touch display to be located at greater distances from the main system MCU or controller. They connect via half-duplex RS485 allowing long-distance communication over a low-cost, compact and flexible cable as well as communication on a bus with multiple external devices. A single cable (for example CAT5e network cable) carries both data and power.
The IDP module is powered from a nominal 24V supply, which reduces the current, and provides more headroom for voltage drop over long distances. This supply is regulated and smoothed internally, providing stable 5V and 3.3V rails for the electronics inside. The module can only be powered via the RJ45 or JST connector (depending on model) and so a PoE injector can be used to connect a 24V power adapter to the RJ45 connector.
Note that the IDP-3510-04A desktop module connects via Wi-Fi and Bluetooth and is powered by a local USB Micro-B 5V power adapter.
System Architecture and Partitioning
The IDP modules also help designers add a graphical touch HMI to products and systems where the main product controller does not have an MCU. For example, this may be an industrial controller which communicates over RS485 but does not have an interface or a software system which can be programmed to control EVE directly.
There are also cases where a product may not be able to accommodate changes. The MCU or processor used may be running very tightly timed control loops, may be at its maximum capacity already in terms of resources, or may have very basic I/O or programmability. It is also possible that the main controller software cannot be changed for certification purposes or that the controller is an accessory for a 3rd party product which has an available UART or RS485 interface.
The IDP modules offer a solution as a self-contained module. The on-board MCU (FT900, RP2040 or ESP32 depending on model) allows the IDP module to take care of the HMI tasks and implementation, via the EVE device, ensuring a responsive experience for users. It runs the custom HMI design which can be developed via our graphical design tools and BSPs (board support packages).
Figure 2: The IDP modules feature an EVE graphics controller and on-board MCU. Note that the peripherals shown vary by model – See Figure 5 for details.
The MCU also facilitates the connection of the IDP module to external devices via an RS485 link (or Wi-Fi and Bluetooth on the IDP-3510-04A). The RS485 communication is fully managed by the onboard MCU, allowing either the use of a standard protocol such as Modbus or the implementation of a custom protocol defined by the developer. The IDP module manages the user interface, receiving commands and data updates via RS485 and sending commands based on user interactions with the HMI. It can therefore be easily tailored to match the requirements of the attached RS485 device(s).
Time to Market
Time to market is another key factor which can challenge designers. Whilst devices such as EVE help keep the BOM and PCB space to a minimum when adding graphical touch display to a product, the design of the enclosure itself along with mounting of the display, PCB and external connections, can be complex and time-consuming.
The IDP modules are supplied in a modern and stylish custom-designed enclosure providing fast and easy integration into products, mounted within buildings or even positioned on desks etc. They are available with display sizes from 3.5” up to 10.1” to suit a range of applications.
Figure 3: The IDP-3510-04A is ideal for rapidly deploying devices for use on desktops etc.
Figure 4: The IDP-1000-04A provides a large 10.1” display with capacitive touch and a range of mounting options
Features of the IDP Modules
The IDP modules also have a range of peripheral devices onboard (depending on model) which can enhance the functionality and the user experience as shown in the table below. Please also refer to the individual IDP module datasheets for more details.
| IDP Module | 
|
|
|
|
|
|
|
| Display size and resolution | 3.5”
320 x 480 |
3.5”
320 x 240 |
4.0”
480 x 480 |
5.0”
800 x 480 |
7.0”
800 x 480 |
7.0”
800 x 480 |
10.1”
1280 x 800 |
| EVE Device | FT811 | FT813 | BT815 | FT813 | BT815 | BT815 | BT817 |
| Touch | Capacitive | None | Capacitive | Capacitive | Capacitive | Capacitive | Capacitive |
| MCU | FT903 | ESP32 | RP2040 | FT903 | FT903 | FT903 | RP2040 |
| Data Interface | RS485
(RJ45 x 2) |
Wi-Fi, Bluetooth, Bluetooth LE | RS485
(JST connector |
RS485
(RJ45 x 2) |
RS485
(RJ45 x 2) |
RS485
(RJ45 x 2) |
RS485
(JST connector |
| Power | 24V
(9 – 24V) |
5V
Micro USB |
24V
(15 – 24V) |
24V
(9 – 24V) |
24V
(9 – 24V) |
24V
(9 – 24V) |
24V
(9 – 24V) |
|
Other Features
|
Smart LED indicator
Audio buzzer ID switch |
USB-UART interface
Smart LED Indicator Audio buzzer User-defined function button |
Audio buzzer
ID switch |
Digital microphone
Ambient light sensor Smart LED indicator Audio buzzer ID switch |
Digital microphone
Ambient light sensor Smart LED indicator Audio buzzer ID switch |
Digital microphone
Ambient light sensor Smart LED indicator Audio buzzer ID switch 13.56MHz RFID Reader |
Time-of-Flight sensor
Ambient light sensor Smart LED Indicator Audio buzzer ID switch |
| Enclosure form factor | Portrait display for wall and panel mounting
|
L-Shaped desktop display | Sleek and modern design for wall and panel mounting
|
5” landscape display in enclosure for wall or panel mounting | 7” landscape display in enclosure for wall or panel mounting | Version of IDP-7000-04A with RFID Reader | Large 10.1” display with sleek and modern design for wall and panel mounting |
Figure 5: Comparison of the IDP modules
Audio Buzzer: Allows the application to play sounds (either built-in or custom sounds converted using the EVE Asset Builder). Play clicks or beeps to acknowledge touch inputs or a range of sounds as notifications and alarms to get the users attention.
Ambient Light sensor: The MCU can use this to sense the ambient light levels which the display is exposed to. It can then adjust the display backlight brightness (via the internal EVE device’s backlight PWM output) to an optimal level for viewing.
Time of Flight sensor: Allows the MCU to detect when a user is in close proximity to the display. The display can be put into a low-power mode when no user is present for a certain amount of time and can be woken up when they approach. This can save power and increase life span by avoiding the display being on when no users are present.
Smart LED indicator: One or two RGB LED light strips integrated into the enclosure, with full control of the colour from the MCU, can be used to provide at-a-glance status indication to users from a distance even when the display is off.
RFID Reader: The integrated reader can be used for user identification and access control, etc.
ID switch: A rotary switch provides a convenient way to set a unique ID or address for each unit and can be read by the firmware on the internal MCU. For example, this can be used to set a unique ID where a number of the IDP panels are used on the same RS485 network.
User defined button: This button on the IDP-3510-04A is read by a GPIO input on the MCU and can be used as a function button by the firmware for accessing various settings, including display functions, brightness adjustment, volume control, and factory reset.
RJ45 in/thru: Some models have RJ45 connectors for both RS485 and power. Two connectors are provided, which are linked inside the IDP, allowing easy daisy-chaining of the panels for systems where multiple display panels are used. Other models have a single JST connection with 5M JST to RJ45 provided.
Capacitive Multi-Touch: Available on all models except IDP-3510-04A, the displays have touch panels supporting up to 5 simultaneous touches, allowing the application to use touch control. The EVE touch engine makes firmware development easy with its tagging and tracking features.
SD Card: The SD card is connected to the MCU. The application code can read files such as bin files containing assets for the user interface (such as images).
Digital Microphone: This allows the MCU to capture audio vis the microphone on the side of the enclosure.
Application Development
Bridgetek’s range of free tools and examples combined with the powerful on-board EVE graphics controller allow comprehensive and capable HMIs to be created and deployed rapidly for the IDP modules.
The EVE Screen Designer offers drag-and-drop layout of the screen content with a wide range of widgets and controls, in addition to the logic to handle user inputs and update the display. The IDP modules can be selected as the target device when creating a new project and the code can be easily deployed to the MCU.
Figure 6: Software development is fast and easy with the EVE Screen Designer
Alternatively, developers may build the application using a code-based approach by leveraging the Board Support Package (BSP) for each module, which is accessible via the Bridgetek GitHub repository. The BSP includes drivers for the different hardware devices onboard, allowing developers to avoid the time needed to create hardware drivers etc. and begin developing the main application immediately.
Figure 7: BSPs for each module save time and effort to speed application development
Applications
Applications include:
- Smart Building and Smart Home systems
- Point of Sales systems
- Vending macines
- Industrial control
- Demonstration platforms
- Advertising and digital signage
- Control panels
- Any many more …
Conclusion
With the new IDP modules from Bridgetek, designers can quickly and easily enhance the way that users interact with their product. Tasks such as mechanical enclosure design, and creation of code libraries for bespoke hardware designs often add significant delays to a project. The IDP modules help engineers avoid these delays, saving time in application development and going to production.
The modules also provide a reliable solution where the there is a large distance between the display panel and the device that it is controlling, or indeed in systems where the main processor cannot accommodate a graphics library and SPI / QSPI connection directly.
Some of the key features of the IDP modules include:
- Range of display sizes from 3.5” to 10.1”
- Bridgetek’s Embedded VIdeo Engine to make HMI development easy
- On-board MCU handles HMI and communicates with external devices
- Supported by free HMI design tools and BSPs
- Fast time to market
The IDP modules are ideal for engineers designing and updating in-house products, design consultancies, and companies developing 3rd party controls for other products and systems.
